1. Field of the Invention
The present invention relates to a cutting device and an image forming apparatus.
2. Description of the Related Art
Conventionally, well-known image forming apparatuses include copying machines, printers, facsimiles and their multifunction peripherals, and generally use an electrophotographic technique. Not only black-and-while image forming apparatuses, but also full-color images forming apparatuses are widely commercialized.
As the image forming apparatuses are used in various fields, high quality images are demanded. Specifically, it is demanded that full-color images have a high degree of uniformity of gloss as one factor for improving the image quality.
Smoothness of an output image is one factor for determining its degree of gloss. In response to such demand, suggested is a technique for transferring a color toner including a thermoplastic resin onto a recording material having a transparent resin as a toner receiving layer made of a thermoplastic resin. Further, the color toner is heated and melts, so as to form a color image thereon (see Japanese Patent Application Laid-Open (JP-A) No. 64-35452 and JP-A No. 05-216322).
According to this image forming method, a cool-separating type of fixing device (hereinafter referred to as a belt fixing unit) having a fixing belt is preferred.
This belt fixing unit includes a fixing belt having a heat resistant film and pressuring/heating a recording material carrying an unfixed toner. In this belt fixing unit, the recording material is separated from the fixing belt after cooling the recording material while being adhered to the fixing belt so as to solidify the toner image thereon (see JP-A No. 04-216580 and JP-A No. 04-3626679).
With this belt fixing unit, the toner image is fixed in a state where it is embedded, into a transparent resin layer of the recording material. The transparent resin and toner image on the surface of the recording material are both solidified in accordance with the surface form of the belt. As a results, the recording material will have an even surface entirely, thus capable of generating a high-gloss color image.
A high-gloss image can be output by means of such a cool-separating type fixing unit. Thus, a high-gloss image of a photographic tone, such as sublimation type or silver-salt type, can be obtained using an image forming apparatus of an electrophotographic technique.
An electrophotographic transfer sheet is proposed as a recording material having a resin layer used in such an image forming apparatus. To form the transfer sheet, a resin layer is coated into a thickness of approximately 20 μm. Note this resin layer mainly has a thermoplastic resin whose glass transformation temperature is equal to for lower than 85° C. (see JP-A No. 2003-084477).
Followings are some problems in the cool-separating type belt fixing unit.
The above publications of JP-A No. 04-216580 and JP-A No. 04-362679 disclose the cool-separating type of the belt fixing unit. In this fixing unit, after a recording material is heated and pressured by a fixing portion, the fixing belt is cooled down, and the recording material is separated therefrom. After the separation, the fixing belt is heated up to a predetermined temperature before it reaches the fixing portion again, and is heated up and pressured again by the fixing portion.
While the fixing belt goes around the above temperature cycle from the heating until the cooling, the fixing belt should be kept long enough to reach the fixing temperature and the separation temperature. As a result, the conveying speed decreases, thereby decreasing the output number in a unit time.
To enhance the output number, the fixing belt may possibly be conveyed at a higher speed. However, in such a case, a great amount of power is required for heating and cooling. Therefore, this method could not easily be realized.
According to a proposal, when a small size of sheet is used in image forming requiring a high-gloss photographic image, many images are formed on a sheet of a larger size, and output images are cut into a predetermined size using a separated cutter. The small size of sheet may, for example, be an L-size (127 mm×89 mm), KG size (152 mm×102 mm), or post-card size (148 mm×100 mm).
Specifically, proposed is a printing system having a post-processor which cuts a resultant object on which an image has been formed by a continuous (serial) paper printer (see JP-A No. 2004-053857). With such a printing system, four images of the above L size, KG size and post-card size can be output using only an A4 size sheet for each case. If the sheet on which images of a plurality of sheets are formed is cut into a predetermined size by a cutting unit, thereby obtaining output images of the predetermined size.
However, according to the above system, while the images are formed by the body machine, the sheet is cut by a different device. Thus, the user needs to cut the sheet on which the pluralities of images are arranged, giving the user some extra work to do.
When the user-desired number of output images differs from the actual number of generated sheets after being cut, a problem is that an unnecessary output object is included in the output sheets. For example, when three images of L size are output using a recording material of A4 size, the three images are arranged in the respective our divisions of the material so as to be output. The recording material of A4 size is cut into, four pieces, thus generating one blank sheet. In such a case, the user needs to dispose this blank sheet, i.e. user needs to do some extra work.